Add crash keys about field trial shared memory errors.

base/memory/shared_memory_mac.cc

Index: base/memory/shared_memory_mac.cc
diff --git a/base/memory/shared_memory_mac.cc b/base/memory/shared_memory_mac.cc
index ec74b0e5525411d476961807a7dfb132df2785e9..e7939b0192cf1382723b5e2cfae0da73347692cf 100644
--- a/base/memory/shared_memory_mac.cc
+++ b/base/memory/shared_memory_mac.cc
@@ -135,10 +135,15 @@ bool SharedMemory::GetSizeFromSharedMemoryHandle(
 // "name == L"". The exception is in the StatsTable.
 bool SharedMemory::Create(const SharedMemoryCreateOptions& options) {
   DCHECK(!shm_.IsValid());
-  if (options.size == 0) return false;
+  if (options.size == 0) {
+    last_error_ = SharedMemoryError::BAD_PARAMS;
+    return false;
+  }
 
-  if (options.size > static_cast<size_t>(std::numeric_limits<int>::max()))
+  if (options.size > static_cast<size_t>(std::numeric_limits<int>::max())) {
+    last_error_ = SharedMemoryError::BAD_PARAMS;
     return false;
+  }
 
   if (options.type == SharedMemoryHandle::MACH) {
     shm_ = SharedMemoryHandle(options.size, UnguessableToken::Create());
@@ -155,30 +160,31 @@ bool SharedMemory::Create(const SharedMemoryCreateOptions& options) {
   ScopedFD readonly_fd;
 
   FilePath path;
-  bool result = CreateAnonymousSharedMemory(options, &fp, &readonly_fd, &path);
+  bool result = CreateAnonymousSharedMemory(options, &fp, &readonly_fd, &path,
+                                            &last_error_);
   if (!result)
     return false;
-
-  if (!fp) {
-    PLOG(ERROR) << "Creating shared memory in " << path.value() << " failed";
-    return false;
-  }
+  DCHECK(fp);  // Should be guaranteed by CreateAnonymousSharedMemory().
 
   // Get current size.
   struct stat stat;
-  if (fstat(fileno(fp.get()), &stat) != 0)
+  if (fstat(fileno(fp.get()), &stat) != 0) {
+    last_error_ = SharedMemoryError::STAT_FAILED;
     return false;
+  }
   const size_t current_size = stat.st_size;
   if (current_size != options.size) {
-    if (HANDLE_EINTR(ftruncate(fileno(fp.get()), options.size)) != 0)
+    if (HANDLE_EINTR(ftruncate(fileno(fp.get()), options.size)) != 0) {
+      last_error_ = SharedMemoryError::TRUNCATE_FAILED;
       return false;
+    }
   }
   requested_size_ = options.size;
 
   int mapped_file = -1;
   int readonly_mapped_file = -1;
   result = PrepareMapFile(std::move(fp), std::move(readonly_fd), &mapped_file,
-                          &readonly_mapped_file);
+                          &readonly_mapped_file, &last_error_);
   shm_ = SharedMemoryHandle(FileDescriptor(mapped_file, false),
                             UnguessableToken::Create());
   readonly_shm_ = SharedMemoryHandle(
@@ -187,12 +193,18 @@ bool SharedMemory::Create(const SharedMemoryCreateOptions& options) {
 }
 
 bool SharedMemory::MapAt(off_t offset, size_t bytes) {
-  if (!shm_.IsValid())
+  if (!shm_.IsValid()) {
+    last_error_ = SharedMemoryError::BAD_PARAMS;
     return false;
-  if (bytes > static_cast<size_t>(std::numeric_limits<int>::max()))
+  }
+  if (bytes > static_cast<size_t>(std::numeric_limits<int>::max())) {
+    last_error_ = SharedMemoryError::BAD_PARAMS;
     return false;
-  if (memory_)
+  }
+  if (memory_) {
+    last_error_ = SharedMemoryError::BAD_PARAMS;
     return false;
+  }
 
   bool success = shm_.MapAt(offset, bytes, &memory_, read_only_);
   if (success) {
@@ -201,6 +213,7 @@ bool SharedMemory::MapAt(off_t offset, size_t bytes) {
                       (SharedMemory::MAP_MINIMUM_ALIGNMENT - 1));
     mapped_memory_mechanism_ = shm_.type_;
   } else {
+    last_error_ = SharedMemoryError::MMAP_FAILED;
     memory_ = NULL;
   }